Oral polio vaccine is divided into trivalent live attenuated vaccine (oral sugar pill), bivalent live attenuated vaccine (oral drops), and in May 2016, the National Health Commission has discontinued the use of oral sugar pill in favor of safer oral drops.
Polio vaccines include live attenuated vaccines (oral sugar pill tOPV, oral drops bOPV), and inactivated vaccines (injection IPV, polio vaccine in Pentavalent).
Live attenuated vaccines are removed from the pathogenicity of the virus, retaining a certain immunogenicity, reproducibility, a certain virulence, so live vaccines can have the risk of infecting vaccinated persons, the emergence of vaccine-associated paralytic polio; inactivated vaccines are inactivated viruses, retaining only their immunogenicity.
The reason for discontinuing the use of oral sugar pills in favor of oral drops is that poliovirus type II has been eliminated worldwide, so only live bivalent attenuated vaccine is needed for prevention.
Poliomyelitis is of great significance in the prevention of polio, and inactivated vaccine has been incorporated into the national immunization plan, and should be vaccinated at regular medical institutions on time.